1. Field of the Invention
The present invention relates generally to a blow-molded container having a base structure which enhances the structural integrity of the container, and more particularly to a non-round base structure having a heel-push-up design.
2. Related Art
Many beverage products are sold to the consuming public in plastic containers such as those that are shown in U.S. Pat. No. 5,005,716 (Eberle), U.S. Pat. No. 4,108,324 (Krishnakumar et al.), and U.S. Pat. No. 4,134,510 (Chang). The design of plastic containers must take into account the container's structural integrity, the manufacturing cost to mass-produce the container, and the aesthetic appearance of the container to the eye of the consumer.
A hot-fillable plastic beverage container must be structurally sound to withstand various forces relating to the so-called “hot-fill” process. Moreover, it must withstand rough handling during transportation to the ultimate consumer. A “hot-fill” process is the procedure by which containers are filled with a beverage at a high temperature after which the containers are capped. As the beverage cools within the container, stresses and strains develop in the container due to changes in the volume of the contents. Containers that store products under pressure, such as carbonated beverages, also experience pressure changes due to changes in ambient temperature. A commercially satisfactory container structure must not only withstand these forces from a structural viewpoint, but it must also present an aesthetically pleasing appearance to the ultimate consumer.
The price of many products sold to the consuming public is affected to an extent by the cost of packaging. With plastic beverage containers, the cost of manufacturing a container is affected by the cost of plastic composing the container. Therefore, if the amount of plastic in a container can be reduced (i.e., a process known as “light weighting”), the cost of manufacturing the container can be reduced commensurately. However, in achieving this goal it is known that the thinner the walls and base of the container become, the greater the need is to utilize imaginative designs to provide a container that is commercially acceptable.
The desire to decrease the amount of plastics used in a container has resulted in the development of different techniques to design containers that have structural integrity with minimal use of plastic. It is known that the shape and location of structural elements such as ribs, hinges, panels, and the like can affect the container's overall structural integrity. While various structural elements molded in the side panel and base structure can afford structural integrity, they must also be visually appealing to the consumer.
Krishnakumar et al ('324) illustrate a rounded container base structure, which employs various structural elements molded into the base that enhances structural integrity. This base design has a series of radially extending ribs, which allow the base structure to withstand a variety of applied forces and which minimize the use of plastic.
Eberle ('716) discloses a round base structure having a central concavity and a convex heel. The heel surrounds the concavity and merges with the concavity and the container sidewall. A plurality of hollow convex ribs, distributed in a symmetrical array, interrupt the outer surface of the concavity and merge smoothly therewith, each rib extending longitudinally in the direction of the heel and downwardly from an inner portion of the concavity. The wall of the bottom structure generally decreases in thickness progressively from the innermost point of the concavity to the sidewall. The structure allows the base to withstand the various stresses and strains applied to the container and also minimizes the use of plastic.
Chang ('510) shows a round base, which employs a series of circumferential ribs in combination with radial ribs to provide the desired degree of structural integrity. The radial ribs intersect all of the circumferential ribs. The various ribs are solid.
The well known 1.75-liter Tropicana Twister® (a registered trademark of Tropicana Products, Inc., 1001 13th Avenue, East Bradenton, Fla. 33506) plastic beverage container has a rounded heel/push-up base design with a very narrow heel surface which functions as the horizontal bearing surface. However, the 1.75-liter Tropicana Twister plastic beverage container contains no vacuum base flex area in its base.
Although the aforementioned containers and base structures may function satisfactorily for their intended purposes, there remains a continuing need for a blow-molded plastic container having a base structure which enhances container structural integrity while requiring a minimum use of plastic. Also, these base structures need to be aesthetically pleasing and be capable of being manufactured in conventional high-speed equipment.